Flap actuator

ABSTRACT

A flap actuator is provided for controlling movement of a flap on a wing of an aircraft. The flap actuator includes a housing having a leading end and a trailing end. A ball nut is rotatably supported in the housing. A motor has a rotatable drive shaft that is rotatable in first and second opposite directions. A gear assembly translates rotation of the drive shaft to the ball nut. A ball screw extends along a longitudinal axis and has a terminal end operatively connectable to the flap. The ball screw is movable between a first retracted in response to rotation of the ball nut in a first direction and a second extended position in response to rotation of the ball nut in a second direction. A one-way roller clutch is operatively connectable to the ball nut. The roller clutch engages the housing and prevents rotation of the ball nut in a first direction in response to a compressive force on the ball screw by the flap. First and second concentric gimbals are positioned about the longitudinal axis adjacent the housing. The gimbals interconnect the housing to the wing.

FIELD OF THE INVENTION

This invention relates generally to aircrafts, and in particular, to aflap actuator for controlling operation of a flap on the wing of anaircraft.

BACKGROUND AND SUMMARY OF THE INVENTION

The maneuverability of an aircraft depends heavily on the movement ofhinged sections or flaps located at the trailing edges of the wings. Byselectively extending and retracting the flaps, the aerodynamic flowconditions of the wings may be influenced so as to increase or decreasethe lift generated by the wings. For example, during the take-off andlanding phases of a flight, the position of the flaps of the aircraftare adjusted to optimize the lift and drag characteristics of the wing.It can be appreciated the reliable operation of the flaps is of criticalimportance to an aircraft.

In large aircraft, a series of flaps are provided on the trailing edgeof each wing. The flaps are raised and lowered in a conventional mannerby a hydraulically actuated linkage of bell cranks, pushrods, andidlers. A flap control lever is provided in the cockpit of the aircraftto control the system mechanically. The flap control lever is connectedby conventional and teleflex cables to a hydraulic actuating mechanism.As is known, these hydraulic actuating mechanisms utilize largecentralized pumps to maintain pressure hydraulic pressure within thesystem. Hydraulic lines distribute the hydraulic fluid under pressure tocorresponding flap actuators. In order to insure the reliability of thesystem, multiple hydraulic lines are run to each flap actuator.

While functional for their intended purposes, these prior hydraulicsystems have certain inherent problems. For example, it is highlydesirable for all systems on an aircraft to be easily serviceable sothat departure of the aircraft will not be delayed while mechanicsattempt to diagnose and repair the aircraft. However, given thecomplexity of the pumps and the lines in the hydraulic system of theaircraft, it is often relatively difficult and costly to diagnose and/orrepair the hydraulic system. Further, the use of multiple hydrauliclines must be run to each flap actuator to ensure redundancy in thesystem is costly, both in terms of weight and money. Hence, it is highlydesirable to provide a redundant, flap actuator control system that issimple to install and service and this is lightweight.

Therefore, it is a primary object and feature of the present inventionto provide a flap actuator that is simple to install and service.

It is a further object and feature of the present invention to provide aflap actuator that incorporates redundant load path design.

It is a still further object and feature of the present invention toprovide a flap actuator that maintains the position of a flap of anaircraft in response to a compression load thereon by the flap.

In accordance with the present invention, a flap actuator is providedfor controlling movement of a flap on a wing of an aircraft. The flapactuator includes a shaft extending along a longitudinal axis and havinga terminal end operatively connectable to the flap. The shaft is movablebetween a first retracted position and a second extended position. Ano-back assembly is operatively connectable to the shaft. The no-backassembly prevents movement of the shaft toward the retracted position inresponse to a compressive force generated by the flap.

The no-back assembly includes a housing for supporting the shaft and afirst gimbal for interconnecting the housing to the wing. A secondgimbal also interconnects the housing to the wing. First and second pinsextend between the housing and the first gimbal, and interconnect thesecond gimbal to the first gimbal and the housing. A mounting pinextends through the first gimbal and is operatively connectable to thewing.

The flap actuator also includes a ball nut engageable with the shaft androtatable about the longitudinal axis. Rotation of the ball nut in afirst direction causes the shaft to move toward the extended position,while rotation of the ball nut in a second direction causes the shaft tomove toward the retracted position. The shaft includes a hollow ballscrew extending along the longitudinal axis and an inner bar extendingthrough the ball screw. A motor having a rotatable drive shaft is alsoprovided. The drive shaft is rotatable in first and second oppositedirections. A gear assembly translates rotation of the drive shaft tothe ball nut. The gear assembly includes a clutch. The clutch disengagesthe drive shaft from the ball nut in response to a predetermined forcethereon.

In accordance with a further aspect of the present invention, a flapactuator is provided for controlling movement of a flap on a wing of anaircraft. The flap actuator includes a housing having a leading end anda trailing end. A ball nut is rotatably supported in the housing. A ballscrew extends along a longitudinal axis and has a terminal endoperatively connectable to the flap. The ball screw movable between afirst retracted position and a second extended position in response torotation of the ball nut. A one-way roller clutch is operativelyconnectable to the ball nut. The roller clutch engages the housing andprevents rotation of the ball nut in a first direction in response to acompressive force on the ball screw by the flap. A gimbal assembly isconnected to the housing and is connectable to the wing.

The gimbal assembly includes a first gimbal for interconnecting thehousing to the wing and a second gimbal for interconnecting the housingto the wing. First and second pins extending between the housing and thefirst gimbal. In addition, the first and second pins interconnect thesecond gimbal to the first gimbal and the housing. The gimbal assemblyalso includes a mounting pin extending through the first gimbal andbeing operatively connectable to the wing.

Rotation of the ball nut in a first direction causes the ball screw tomove toward the extended position. Rotation of the ball nut in a seconddirection causes the ball screw to move toward the retracted position. Amotor having a rotatable drive shaft is provided. The drive shaft isrotatable in first and second opposite directions. A gear assemblytranslates rotation of the drive shaft to the ball nut. The gearassembly includes a clutch that disengages the drive shaft from the ballnut in response to a predetermined force thereon. An inner bar extendsthrough the ball screw.

In accordance with a still further aspect of the present invention, aflap actuator is provided for controlling movement of a flap on a wingof an aircraft. The flap actuator includes a housing having a leadingend and a trailing end. A ball nut is rotatably supported in thehousing. A motor has a rotatable drive shaft that is rotatable in firstand second opposite directions. A gear assembly translates rotation ofthe drive shaft to the ball nut. A ball screw extends along alongitudinal axis and has a terminal end operatively connectable to theflap. The ball screw is movable between a first retracted in response torotation of the ball nut in a first direction and a second extendedposition in response to rotation of the ball nut in a second direction.A one-way roller clutch is operatively connectable to the ball nut. Theroller clutch engages the housing and prevents rotation of the ball nutin a first direction in response to a compressive force on the ballscrew by the flap. First and second concentric gimbals are positionedabout the longitudinal axis adjacent the housing. A first pin extendsthrough the first and second gimbals and being operatively connected tothe housing.

A second pin may also extend through the first and second gimbals andbeing operatively connected to the housing and a mounting arrangement isprovided for interconnecting the first gimbal to the wing. It iscontemplated for the first and second gimbals to have a generallyrectangular configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings furnished herewith illustrate a preferred construction ofthe present invention in which the above advantages and features areclearly disclosed as well as others which will be readily understoodfrom the following description of the illustrated embodiment.

In the drawings:

FIG. 1 is an isometric view of a flap actuator in accordance with thepresent invention mounted on a wing of a conventional aircraft;

FIG. 2 is an isometric view of the flap actuator of the presentinvention;

FIG. 3 is a cross-sectional view of the flap actuator of the presentinvention taken along line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view of a flap actuator of the presentinvention taken along line 4-4 of FIG. 3; and

FIG. 5 is a cross-sectional view of a flap actuator of the presentinvention taken along line 5-5 of FIG. 2.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIGS. 1-2, a flap actuator in accordance with the presentinvention is generally designated by the reference numeral 10. As isconventional, an aircraft includes wing 12 projecting laterally from thefuselage (not shown). Wing 12 includes a forward end and a trailing end14. Trailing end 14 of flap 18 includes flap receiving recess 16 formedtherein for receiving flap 18. Flap receiving recess 16 in trailing end14 of wing 12 is defined by first and second generally parallel sides 20and 22, respectively. Trailing ends 20 a and 22 a of corresponding sides20 and 22, respectively, intersect trailing edge 14 of wing 12. Leadingends 20 b and 22 b of corresponding first and second sides 20 and 22,respectively, intersect frame member 24 of wing 12. Frame member 24projects laterally from and is operatively connected to the fuselage ofthe aircraft.

Flap 18 includes first side 26 pivotably connected to side 20 of wing 12and second side 28 pivotably connected to side 22 of wing 12. As isconventional, flap 18 is pivotable about a longitudinal axis adjacent toand parallel to the leading edge 30 of flap 18 and movable between anextended and a retraction position. Flap actuator 10 interconnects flap18 adjacent the leading edge 30 thereof to frame member 24 of wing 12 inorder to control movement of flap 18.

Flap actuator 10 includes a brushless DC motor 32 rigidly connected tohousing 124 in any suitable manner such as bolts or the like. Motor 32is electrically coupled to a controller for receiving electrical powerand converting the same into mechanical power. Motor 32 includes a driveshaft (not shown) rotatable in first and second directions in accordancewith instructions received from the controller. It is intended that themechanical power generated by motor 32 be transmitted to ball screw 98through spur gear assembly 36, for reasons hereinafter described. It isnoted that in the drawings, flap actuator 10 is orientated such thatmotor 32 projects away from the fuselage of the aircraft. It can beappreciated that flap actuator 10 may be orientated such that motor 32projects toward the fuselage of the aircraft without deviating from thescope of the present invention.

Referring to FIG. 4, spur gear assembly 36 includes clutch gear 40mounted on clutch shaft 44 extending along a longitudinal axis. Clutchshaft 44 includes a first end 44 a rotatably supported by bearing cage46 and a second opposite end 44 b supporting by bearing cage 48. Clutchshaft 44 further includes clutch plate 50 projecting radially from alocation adjacent first end 44 a. A first set of roller bearings 52 arecaptured between clutch plate 50 and a first side of clutch gear 40. Asecond set of roller bearings 54 are captured between a second side ofclutch gear 40 and a first side of thrust plate 56 which extends aboutclutch shaft 44. Belleville spring 58 is captured between a second sideof thrust plate 56 and adjustment nut 60 threaded onto clutch shaft 44.Pinion 62 projects radially from clutch shaft 44 adjacent second end 44b thereof.

When assembled, it is intended for belleville spring 58 to compressthrust plate 56, first and second roller bearings 52 and 54,respectively, and clutch gear 40 against clutch plate 50 so as totranslate rotation (or more precisely, power) of clutch gear 40 toclutch shaft 44 under normal operating positions. In operation, theouter surface of drive shaft of motor 32 meshes with and drives clutchgear 40 in a user desired direction. If the torque generated on clutchgear 40 is below a predetermined threshold, rotation of clutch gear 40is translated to clutch shaft 44. In the event that the torque on clutchgear 40 extends a predetermined threshold (e.g., if a downstreamcomponent of flap actuator 10 is locked in position), clutch gear 40slips on clutch shaft 44 such that rotation of clutch gear 40 is nottranslated to clutch shaft 44. The torque threshold may be adjusted byvarying the spring force generated by belleville spring 58 on thrustplate 56 via adjustment nut 60.

Pinnion 62 meshes with and drives spur gear 64. Inner diameter of spurgear 64 is keyed to the outer diameter of bevel shaft 66. Bevel shaft 66is rotatably supported by first and second bearing cages 70 and 72,respectively. Washer 74 and nut 76 combination are mounted on first end78 of bevel shaft 66 to maintain first and second bearing cages 70 and72, respectively, and spur gear 64 thereon. Second end 80 of bevel shaft76 includes enlarged bevel pinion 82 projecting therefrom. Bevel pinion82 meshes with teeth 84 of bevel gear 86 in order to translate rotationof bevel pinion 82 to bevel gear 86.

Referring to FIG. 3, bevel gear 86 has a splined inner surface 88 thatmeshes with outer surface 90 of ball nut 92. Threads 94 along the innerdiameter of ball nut 90 mesh with threads 96 along the outer surface ofball screw 98 for reasons hereinafter described. Ball screw 98 furtherincludes central passageway 98 a adapted for receiving inner rod 99therethrough. It is intended for inner rod 99 to maintain the integrityof ball screw 98 in the event of a fracture of ball screw 98. Inner rod99, and hence ball screw 98, extends along a longitudinal axis andincludes enlarged head 100 on a first end 102 thereof. Reinforcedaperture 104 extends through head 200 of ball screw 98. As best seen inFIG. 1, head 100 of ball screw 98 is interconnected to wing 18 adjacentleading edge 30 thereof through aperture 104. Second end 105 of innerrod 99 includes a seal 107 and nut 109 combination secured thereon formaintaining ball screw 98 on inner rod 99 and preventing unwantedmaterial from entering the central passageway 98 a.

In order to prevent axial movement (from right to left in FIG. 3) ofball screw 98 under pressure of a compressive load on the surfaces offlap 18, and hence movement of flap 18 during operation of an aircraft,no-back assembly 106 is provided. No-back assembly 106 includes trailingthrust plate 108 and is positioned against shoulder 110 projectingradially from ball nut 92. Skewed roller 112 is positioned betweentrailing thrust plate 108 and leading thrust plate 114. Leading thrustplate 114 is generally tubular and includes an inner diameter about theouter periphery of ball nut 92 and plate element 116 projecting radiallyfrom a first end thereof. Thrust washer 118 and thrust bearing 120 arepositioned between support surface 122 of housing 124 and plate element116 of thrust plate 114. One-way roller clutch 126 is disposed betweenouter surface 128 of thrust plate 114 and inner surface 130 of housing124.

Roller clutch 126 only allows rotation of thrust plate 114 in a singledirection, e.g., clockwise. As such, with ball screw under a compressiveload, thrust plate 108 engages skewed roller 112 and urges skewed rolleragainst thrust bearing 120. Due to the friction developed between ballnut flange 110, thrust plate 108, skewed roller 112 and thrust plate114, clutch roller 126 prevents further rotation of ball screw 98 in theclockwise direction.

Housing 124 is interconnected to frame element 124 of wing 12 by primaryand secondary gimbals 134 and 136, respectively, FIG. 5. As best seen inFIG. 3, it is contemplated for housing 124 to include main portion 125and secondary portion 127 attached thereto by a plurality of throughbolts 129, FIG. 2. Housing 124 includes spaced upper primary gimbalmounting tabs 138 and 140, respectively, projecting from leading end 125a of main portion 125 of housing 124. Upper primary gimbal mounting tabs138 and 140, respectively, are generally U-shaped and includecorresponding apertures 142 and 144, respectively, therethrough. Spacedlower primary gimbal mounting tabs 146 and 148, respectively, projectfrom leading end 125 a of main portion 125 of housing 124. Lower primarygimbal mounting tabs 146 and 184 are generally U-shaped and includecorresponding apertures 150 and 152, respectively therethrough.Apertures 142 and 144 through upper primary gimbal mounting tabs 138 and140, respectively, are axially aligned with apertures 150 and 152 thoughcorresponding lower primary gimbal mounting tabs 146 and 148,respectively, for reasons hereinafter described.

Housing 124 further includes spaced upper secondary gimbal mounting tabs154 and 156, respectively, extending from leading end 127 a of secondaryportion 127 of housing 124. Upper secondary gimbal mounting tabs 154 and156 are generally U-shaped and include corresponding apertures 158 and160, respectively, therethrough. Spaced lower secondary gimbal mountingtabs 162 and 164, respectively, project from leading end 127 a ofsecondary portion 127 of housing 124. Lower secondary gimbal mountingtabs 162 and 164 are generally U-shaped and include correspondingapertures 166 and 168, respectively, therethrough. Apertures 158 and 160through upper secondary gimbal mounting tabs 154 and 156, respectively,and apertures 166 and 168 through lower secondary gimbal mounting tabs162 and 164, respectively, are axially aligned with each other and withapertures 142, 144, 150 and 152.

Referring back to FIG. 5, primary gimbal 134 has a generally squareconfiguration and is defined by upper and lower walls 170 and 172,respectively having apertures 176 and 178, respectively, therethrough.Primary gimbal 134 is further defined by first and second sidewalls 177and 179, respectively, having corresponding apertures (not shown)therethrough, for reasons hereinafter described.

Secondary gimbal 136 also has a square-like configuration and includesupper and lower walls 180 and 182, respectively. Upper and lower walls180 and 182, respectively, of secondary gimbal 136 include correspondingapertures 184 and 186, respectively therethrough. In addition, secondarygimbal 136 is defined by first and second sidewalls 188 and 190,respectively, having corresponding apertures (not shown) therethrough.

In order to mount housing 124 to wing 12, upper gimbal 134 is positionedsuch that upper wall 170 of primary gimbal 134 is received between upperprimary gimbal mounting tabs 138 and 140 and such that lower wall 172 ofprimary gimbal 134 is received between lower primary gimbal mountingtabs 146 and 148. In addition, aperture 176 through upper wall 170 ofprimary gimbal 134 is axially aligned with apertures 142 and 144 throughupper primary gimbal mounting tabs 138 and 140, respectively, and suchthat aperture 178 through lower wall 172 of primary gimbal 134 isaxially aligned with apertures 150 and 152 through primary gimbalmounting tabs 146 and 148, respectively.

Secondary gimbal 136 is positioned such that upper wall 180 of secondarygimbal 136 is received between upper secondary gimbal mounting tabs 154and 156 and such that lower wall 182 of secondary gimbal 136 is receivedbetween lower secondary gimbal mounting tabs 146 and 148. Aperture 184through upper wall 180 of secondary gimbal 136 is axially aligned withapertures 158 and 160 through upper secondary gimbal mounting tabs 154and 156, respectively, and aperture 186 through lower wall 182 ofsecondary gimbal 136 is axially aligned with apertures 166 and 168through lower secondary gimbal mounting tabs 162 and 164, respectively.

Once primary and secondary gimbals 134 and 136, respectively, arepositioned as heretofore described, upper pin 190 is inserted throughaperture 142 in upper primary gimbal mounting tab 138; aperture 176through upper wall 170 of primary gimbal 134; aperture 144 through upperprimary gimbal mounting tab 140; aperture 158 through upper secondarygimbal mounting tab 154; aperture 184 through upper wall 180 ofsecondary gimbal 136; and aperture 160 through upper secondary gimbalmounting tab 156. In addition, pin 192 is inserted through aperture 150in lower primary gimbal mounting tab 146; aperture 178 through lowerwall 172 of primary gimbal 134; aperture 152 through lower primarygimbal mounting tab 148; aperture 166 through lower secondary gimbalmounting tab 162; aperture 186 through lower wall 182 of secondarygimbal 136; and through aperture 168 through lower secondary gimbalmounting tab 164. Thereafter, primary gimbal 134 is positioned withinmounting bracket 194 projecting in a trailing direction from frameelement 24 of wing 12. Spherical bearings incorporating a mounting pinare seated in the aperture in sidewall 177 of primary gimbal 134 and inthe aperture in sidewall 188 of secondary gimbal 136 to rigidly connectflap actuator 10 to mounting bracket 194. Similarly, spherical bearingsincorporating a mounting pin are seated in the aperture in sidewall 179of primary gimbal 134 and in the aperture in sidewall 190 of secondarygimbal 136 to rigidly connect flap actuator 10 to bracket 194.

In operation, a controller, responsive to pilot control, actuates motor32 so as to rotate the drive shaft in a user desired direction. Spurgear assembly 36 translates rotation of the drive shaft to bevel gear 86which, in turn, rotates ball nut 92 about the longitudinal axis of innerrod 99. Rotation of ball nut 92 is translated to ball screw 98 which, inturn, moves linearly along the longitudinal axis of inner rod 99. By wayof example, rotation of ball nut 92 in a clockwise direction causes ballscrew 98 to move in a first linear direction and rotation of ball nut 92in a counterclockwise direction causes ball screw 98 to move in a secondopposite linear direction. In such manner, ball screw 98 may be movedfrom an extended position to a retracted position, thereby allowing theposition of flap 10 to be adjusted.

During operation of the aircraft, a compressive force (from right toleft in FIG. 3) may be provided on first end 102 of inner rod 99 and onball screw 98 by flap 18. This compressive force is translated throughno-back assembly 106, as heretofore described, to housing 124.Thereafter, the compressive load is translated through pins 190 and 192to primary and second gimbals 134 and 136, respectively, and though thespherical bearings of the primary and second gimbals 134 and 136,respectively, to wing 18. It can be appreciated that the arrangement offlap actuator 10 provides redundant load sharing of any compressiveforce generated by a load on flap 18. For example, the load may betranslated solely by ball screw 98 if inner rod 99 is disabled andvisa-versa. Similarly, the load may be translated solely by secondaryportion 127 of housing 124 if main portion 125 of housing 124 isdisabled and visa-versa or the load may be translated solely bysecondary gimbal 136 if primary gimbal 134 is disabled or visa-versa.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter that is regarded as theinvention.

1. A flap actuator for controlling movement of a flap on a wing of anaircraft, comprising: a shaft extending along a longitudinal axis andhaving a terminal end operatively connectable to the flap, the shaftmovable between a first retracted position and a second extendedposition; and a no-back assembly operatively connectable to the shaft,the no-back assembly preventing movement of the shaft toward theretracted position in response to a compressive force generated by theflap; and including: a housing for supporting the shaft; first andsecond concentric gimbals; first and second pins extending through thehousing and the first and second gimbals; and first and second mountingpins extending through the first and second gimbals and beingoperatively connectable to the wing.
 2. The flap actuator of claim 1further comprising a ball nut engageable with the shaft and rotatableabout the longitudinal axis, wherein: rotation of the ball nut in afirst direction causes the shaft to move toward the extended position;and rotation of the ball nut in a second direction causes the shaft tomove toward the retracted position.
 3. The flap actuator of claim 2further comprising; a motor having a rotatable drive shaft, the driveshaft rotatable in first and second opposite directions; and a gearassembly for translating rotation of the drive shaft to the ball nut. 4.The flap actuator of claim 3 wherein the gear assembly includes aclutch, the clutch disengaging the drive shaft from the ball nut inresponse to a predetermined force thereon.
 5. The flap actuator of claim3 wherein the shaft includes a hollow ball screw extending along thelongitudinal axis and an inner bar extending through the ball screw.